How Long Should Your AC Run Per Cycle?
On a typical Denver summer day, your AC should run in cycles of 15-20 minutes, about 2-3 times per hour. On the hottest days (95°F+), it might run longer, but it should still cycle off periodically. If your AC literally never stops, that's a sign something needs attention.
1. Dirty Air Filter (Easy DIY Fix)
This is the most common cause and the easiest to fix. A clogged filter restricts airflow, forcing your system to run longer to reach the set temperature. Pull out your filter and hold it up to the light — if you can't see through it, replace it immediately. Filters cost $5-15 at any hardware store.
2. Thermostat Set Too Low
If your thermostat is set to 68°F and it's 98°F outside, your system may simply not be powerful enough to reach that temperature. The Department of Energy recommends 78°F for a good balance of comfort and efficiency. Try raising your thermostat a few degrees and see if the system starts cycling normally.
3. Dirty Condenser Coils (Outside Unit)
Your outdoor unit needs clear airflow to release heat. If the coils are covered in dirt, grass clippings, or cottonwood fluff (very common along the Front Range in June), your system has to work much harder. You can gently spray the outdoor unit with a garden hose to clean it. Make sure to turn the system off first.
4. Refrigerant Leak (Needs a Pro)
Low refrigerant means your AC can't absorb enough heat from indoor air. The system runs and runs but never satisfies the thermostat. Signs include ice forming on the refrigerant lines, warm air from vents, or a hissing sound near the outdoor unit. This requires a licensed technician — refrigerant isn't something you can buy or add yourself.
5. Undersized System
If your AC has always seemed to struggle on hot days, it may be too small for your home. This is especially common in Denver-area homes that have had additions, finished basements, or converted garages. An undersized system will run constantly on hot days because it physically cannot produce enough cooling. A load calculation by a technician can determine if your system is properly sized.
6. Aging Equipment
AC systems lose efficiency as they age. A system that's 12-15+ years old may run significantly longer than it did when new, even with regular maintenance. If your system is in that age range and running nonstop, it may be more cost-effective to replace it than to keep paying high electric bills.
What to Do Right Now
Check your filter first — it takes 30 seconds. Then check your thermostat setting. If both are fine, look at your outdoor unit for visible dirt or debris. If none of that helps, call a professional before the system suffers additional damage from overworking.